Solar power generation is becoming a progressively larger source of energy throughout the world. Solar power generation systems typically include one or more photovoltaic arrays (PV arrays) having multiple interconnected solar cells that convert solar energy into DC power through the photovoltaic effect. In order to interface the output of the PV arrays to a utility grid, a solar converter is needed to change the DC current and DC voltage output of the PV array into a 60/50 Hz AC current waveform that feeds power to the utility grid.
Various solar power converters exist for interfacing the DC output of a PV array into AC power. One implementation of a solar power converter consists of two stages, a boost converter stage and an inverter stage. The boost converter controls the flow of DC power from the PV array onto a DC bus. The inverter converts the power supplied to the DC bus into an AC current and AC voltage that can be output to the AC grid.
Existing solar power converters utilize control systems to regulate the boost converter and the inverter to compensate for various system variables, such as AC grid voltage magnitude, voltage drops across power devices, such as insulated gate bipolar transistors (IGBTs), diodes and reactors used in the solar power converter, transformers and conductors used in the solar power collection system, and other system variables. To accommodate a normal working range of grid voltage, such as, for instance ±10% of nominal grid voltage, the control system will typically regulate the DC bus voltage of the solar power converter to operate at a fixed DC bus voltage setpoint, such as about 110% of the nominal AC grid voltage. The use of a fixed DC bus voltage setpoint, however, does not optimize the efficiency of the solar power converter, often resulting in higher semiconductor junction temperatures for the IGBTs and diodes of the solar power converter and in higher harmonic frequencies output to the AC grid. This is particularly true when the AC grid voltage is less than the voltage of the DC bus voltage.
Thus, there is a need for a solar power converter that regulates DC bus voltage to increase the efficiency of the solar power converter that overcomes the above disadvantages.